Machining Fundamentals
76
leg. The legs should drag slightly when moved in
and out, or from side to side.
Considerable skill is required to make accurate
measurements with a caliper. See Figure 4-56. Much
depends upon the machinist’s sense of touch. With
practice, measurements with accuracy of 0.003″
(0.07 mm) can be made. However, a micrometer or
Vernier caliper is preferred and must be utilized
when greater accuracy is required.
4.7.2 Telescoping Gage
A telescoping gage is intended for use with a
micrometer to determine internal dimensions,
Figure 4-57. Sets of telescoping gages with varying
ranges are available, Figure 4-58.
To use a telescoping gage, compress the contact
legs. The legs telescope within one another under
spring tension. Insert the gage into the hole and
allow the legs to expand, Figure 4-59. After the
proper fitting is obtained, lock the contacts into
position. Remove the gage from the hole and make
your reading with a micrometer, Figure 4-60.
4.7.3 Small Hole Gage
A small hole gage is used to measure openings
that are too small for a telescoping gage, Figure
4-61. The contacts are designed to allow accurate
Figure 4-53. Using a radius gage. A—Various ways a radius
gage can be used. B—Using a radius gage holder.
(L. S. Starrett Co.)
Figure 4-54. Inside and outside calipers. (L. S. Starrett Co.)
Figure 4-55. The outside caliper is read with a steel rule.
B
A